Who is using I2S cables?

I've been reading / watching info and trying to learn about I2S. Several manufacturers offer I2S connections (Topping, Pro-Ject, Jay's, Denafrips, Singxer, Raspberry Pi?...). I2S has been used internally for years (mainly internal CD to DAC connections) but some components have I2S connections. So, I'm confused and curious. 

1. Are you using I2S cables? What has been your experience? 
2. What components are you using I2S to connect?
3. Are you using an HDMI cable or so-called bonafide I2S?
4. Where did you purchase your I2S cable(s)?

Thanks!